Epidemiology of toxoplasmosis: role of the tick Haemaphysalis longicornis

Yongzhi Zhou, Houshuang Zhang, Jie Cao, Haiyan Gong, Jinlin Zhou

Toxoplasma gondii infection is mainly caused by ingestion of water or food that is contaminated with oocysts excreted by cats, or by eating raw meat containing T. gondii tissue cysts. However, oral transmission does not explain the common occurrence of toxoplasmosis in a variety of hosts, such as herbivorous animals, birds, and wild rodents. Little information exists on the maintenance of T. gondii parasites in nature and routes of transmission to domestic and wild animal hosts. Therefore, this study evaluated the role of Haemaphysalis longicornis ticks in the epidemiology of toxoplasmosis. The real-time polymerase chain reaction (qPCR) technique was used to detect the presence of T. gondii DNA in ticks collected from the field. To observe the amount of dynamic changes of T. gondii in the tick's body and its infectivity, microinjection of green fluorescence parasites was performed. Under laboratory conditions, we evaluated if H. longicornis ticks were infected with T. gondii and their potential to transmit the infection to other hosts using traditional parasitological methods coupled with molecular detection techniques. The infection rates of T. gondii parasites among field-collected adult and nymph H. longicornis ticks were 11.26 % and 5.95 %, respectively. T. gondii can survive and remain infective in a tick's body for at least 15 days. We found that blood feeding of infected ticks did not transmit T. gondii to hosts, however, ingestion of infected ticks may be a transmission route between ticks and other common hosts. The T. gondii infection in ticks could serve as a reservoir for toxoplasmosis transmission.